The pro-choice advocate needs to justify a morally relevant distinction between fetuses and adults in order to justify abortion. In the face of this difficulty some will simply assert that all distinctions attempting to justify protecting human life are arbitrary anyway. We basically protect humans rather than other animals because we have the power to do so. So how can the pro-choicer be accused of being arbitrary when the distinction between humans and animals is already arbitrary?
I thought this was a formidable objection for a non-theist. But bd showed that it really isn't. Here is how he responds:
The diseases and disorders that we fear most are those that are extremely painful and those that affect our minds. Now pain is something that we have in common with animals, so let’s ignore those for the moment. What is it about diseases that affect our minds that we find so terrifying? After all, many insane people and Alzheimer’s patients appear to be quite happy. And some madmen have very interesting, entertaining, and pleasant personalities.
Clearly what we fear is the loss of our reason – our ability to make sense of, or understand, the world by means of abstract concepts. When anyone loses this ability, for example by going mad or becoming a victim of Alzheimer’s, we feel that they have in a real sense lost their humanity: they are no longer rational beings. The case of Alzheimer’s victims is particularly poignant because the loss is gradual, which means that the victims are aware to some extent (especially in the early stages) of what is happening to them.
Even a partial disappearance of this gift is felt as an inestimable loss. If someone suffers an accident that changes his personality we may find this sad, but not always: the new personality may be an improvement over the old one. But if the accident reduces him from being a highly intelligent person to a moron it is always considered a tragedy. And any parent will grieve to learn that his or her child is an imbecile, or even that it has Down’s syndrome. The last point is especially telling, because Down’s children tend to be very loving, trusting, and well-behaved, and they seem to be quite happy so long as they are cared for reasonably well. It is true that they also tend to have physical problems, but this is not the main source of the parents’ grief: it is that they are very likely to have serious intellectual deficiencies.
In fact, even our fear of extremely painful diseases is based to some extent on the fact that excessive pain can impair or even destroy our ability to reason. It is quite common for people with less intense (but sometimes quite serious) pain to refuse to take painkillers because they tend to fog the mind. They would rather be able to think clearly than be free of pain.
Although we have no experience of rational beings other than humans, it seems very likely that any rational being would have pretty much the same attitude toward losing his reason. It seems inconceivable that anyone who has experienced what it is to be a rational being will be indifferent to losing this precious gift. It is also pretty much universally believed that, if a being who does not have this gift were to receive it, he would be extremely grateful for it and would not willingly return to his original condition. This is illustrated wonderfully in the movies Awakenings and Charly. It is also captured in the old saying that it is better to be Socrates dissatisfied than a pig satisfied. We feel confident that even the pig would agree if it were capable of understanding the difference between itself and Socrates.
So although it might be said that the value we place on rationality cannot be demonstrated to be “correct” by pure logic, it is a value that appears to be inherent in the very nature of a rational being. Thus the distinction between beings who are capable of reason and those who are not, far from being “arbitrary”, is based on the most fundamental nature of things. If this distinction is not justified, no distinction is justified.